Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is a malignancy of B-lymphocytes in the blood, bone marrow, and lymph nodes with a characteristic immunophenotype. The recent WHO classification discusses CLL/SLL as an entity but notes that the term SLL is restricted to cases with the tissue morphology and immunophenotype of CLL, but which are non-leukemic (WHO Classification of Tumours. Tumours of Haemotopoietic and Lymphoid Tissue. Edited by Jaffe, Harris, Stein, Vardiman. IARC Press 2001). The clinical course of CLL is quite varied. While some patients have a chronic lymphocytosis without any need for therapeutic interventions, other patients may die rapidly despite aggressive treatment. The classic staging systems provide only limited prognostic information in newly diagnosed patients.
Recently, the presence or absence of somatic mutations in the immunoglobulin (Ig) variable region genes has been shown to distinguish between two disease subsets conferring important prognostic information. A median survival of 95 months was found in patients with unmutated Ig genes versus 293 months in patients with mutated Ig genes (Hamblin, Blood 94(6):1848-1854, 1999). Unfortunately, the ability to sequence Ig genes is not available in most clinical laboratories.
In addition to mutated Ig genes, several other potential diagnostic or prognostic markers have been identified for CLL, as well as for other small B-cell lymphomas. By way of example, these include CD10, CD20, CD21, CD23 (including serum CD23), CD38, CD69, CD43, FMC-7, and BCL-6. The research and medical communities are actively searching for good prognostic markers, but as yet no definitive markers have been identified.